Heart Rate Variability and Risk of All-Cause Death and Cardiovascular Events in Patients With Cardiovascular Disease: A Meta-Analysis of Cohort Studies

Researchers combined results from cohort studies, which follow groups of people over time. The participants had cardiovascular disease, meaning conditions affecting the heart or blood vessels. The studies compared heart-rate variability, the small changes in time between heartbeats, with later deaths from any cause and heart-related events such as heart attacks or strokes. Overall, lower heart-rate variability was linked with higher risks. Because these were observational studies, the results show an association, not proof that low variability causes those outcomes.

What this means for you: You can treat heart-rate variability as a possible health signal, not a diagnosis or a reason by itself to buy a wearable. Follow proven heart-care advice and discuss unusual readings with a clinician, especially if you already have heart disease.